U.S. patent application number 14/952633 was filed with the patent office on 2016-12-01 for control system and control method for fail safety of mdps.
This patent application is currently assigned to Hyundai Motor Company. The applicant listed for this patent is Hyundai Motor Company. Invention is credited to Min Woo Han, Jong Ho Lee, Yang Soo Noh, Yoon Kab Noh.
Application Number | 20160347351 14/952633 |
Document ID | / |
Family ID | 56950071 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160347351 |
Kind Code |
A1 |
Noh; Yoon Kab ; et
al. |
December 1, 2016 |
CONTROL SYSTEM AND CONTROL METHOD FOR FAIL SAFETY OF MDPS
Abstract
Disclosed are a control system and a control method for fail
safety of a motor driven power steering (MDPS). The system may
include a straight motion/turning determination module for
determining whether a vehicle is in a straight motion or turning
based on a steering angle of a steering wheel, a steering torque of
the steering wheel and a vehicle speed of the vehicle, a fail
determination module for determining whether an MDPS fail occurs
based on a steering torque of a driver and a motor torque of the
MDPS if the vehicle is in the straight motion, a fail type
determination module for determining a type of the MDPS fail using
a yaw rate change rate if the MDPS fail occurs, and a yaw rate
change rate detection module for inputting the yaw rate change rate
to the fail type determination module.
Inventors: |
Noh; Yoon Kab; (Seongnam-Si,
KR) ; Lee; Jong Ho; (Incheon, KR) ; Noh; Yang
Soo; (Hwaseong-Si, KR) ; Han; Min Woo; (Seoul,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hyundai Motor Company |
Seoul |
|
KR |
|
|
Assignee: |
Hyundai Motor Company
Seoul
KR
|
Family ID: |
56950071 |
Appl. No.: |
14/952633 |
Filed: |
November 25, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60W 2510/202 20130101;
B60W 2520/10 20130101; B62D 15/021 20130101; B62D 1/286 20130101;
B60W 40/114 20130101; B60W 50/029 20130101; B62D 5/0481
20130101 |
International
Class: |
B62D 5/00 20060101
B62D005/00; B60W 40/114 20060101 B60W040/114; B62D 15/02 20060101
B62D015/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 29, 2015 |
KR |
10-2015-0075819 |
Claims
1. A control system for fail safety of a motor driven power
steering (MDPS), the control system comprising: a straight
motion/turning determination module for determining whether a
vehicle is in a straight motion or turning based on a steering
angle of a steering wheel, a steering torque of the steering wheel
and a vehicle speed of the vehicle; a fail determination module for
determining whether an MDPS fail occurs based on a steering torque
of a driver and a motor torque of the MDPS, if the straight
motion/turning determination module determines that the vehicle is
in the straight motion; a fail type determination module for
determining a type of the MDPS fail using a yaw rate change rate,
if the fail determination module determines that the MDPS fail
occurs; and a yaw rate change rate detection module for inputting
the yaw rate change rate to the fail type determination module.
2. The control system of claim 1, further comprising a motor safety
state transition control unit for switching off an MDPS motor
according to determination results of the fail determination module
and the fail type determination module.
3. The control system of claim 1, wherein when the vehicle speed is
a predetermined value or more, the straight motion/turning
determination module determines whether the vehicle is in the
straight motion or turning based on absolute magnitudes of the
steering torque and the steering angle that have been input.
4. The control system of claim 1, wherein the fail determination
module: multiplies the steering torque by the motor torque when the
vehicle is in the straight motion to obtain a calculated value;
integrates the calculated value over a period of time to obtain an
integrated value; and determines that the MDPS fail occurs when the
integrated value is a first threshold value or more and the motor
torque of the MDPS increases non-proportionally to a second
threshold value or more at the same time.
5. The control system of claim 1, wherein the fail type
determination module determines a self-steering state when the yaw
rate change rate is a third threshold value or more, and determines
a no-steering state when the yaw rate change rate is less than the
third threshold value.
6. The control system of claim 1, wherein the yaw rate change rate
detection module estimates the yaw rate change rate using the
vehicle speed and the steering angle.
7. A control method for fail safety of a motor driven power
steering (MDPS), the control method comprising: determining whether
a vehicle is in a straight motion or turning based on a steering
angle of a steering wheel, a steering torque of the steering wheel
and a vehicle speed of the vehicle; determining whether an MDPS
fail occurs using a steering torque of a driver and a motor torque
of the MDPS, if the straight motion/turning determination module
determines that the vehicle is in the straight motion; and
determining a type of the MDPS fail by detecting a yaw rate change
rate, if it is determined that the MDPS fail occurs.
8. The control method of claim 7, further comprising switching off
an MDPS motor according to determination results of the fail
determination and the fail type determination.
9. The control method of claim 7, wherein when the vehicle speed is
a predetermined value or more, determining whether the vehicle is
in a straight motion or turning is based on absolute magnitudes of
the steering torque and the steering angle.
10. The control method of claim 7, wherein the fail determination
comprises: multiplying the steering torque by the motor torque when
the vehicle is in the straight motion to obtain a calculated value;
integrating the calculated value over a period of time to obtained
an integrated value; and determining that the MDPS fail occurs when
the integrated value is a first threshold value or more and the
motor torque of the MDPS increases non-proportionally to a second
threshold value or more at the same time.
11. The control method of claim 7, wherein in the fail type
determination, a self-steering state is determined when the yaw
rate change rate is a third threshold value or more, and a
no-steering state is determined when the yaw rate change rate is
less than the third threshold value.
12. The control method of claim 7, wherein a yaw rate change rate
is calculated based on the vehicle speed and the steering angle
signal using Yaw rate = V x L + K us V x 2 g .delta. f ,
##EQU00003## wherein V.sub.x denotes a vehicle speed, L denotes a
wheel base, K.sub.us denotes an under steer constant, g denotes an
acceleration of gravity, and .delta..sub.f denotes a steering
angle.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority of Korean Patent
Application Number 10-2015-0075819 filed May 29, 2015, the entire
contents of which application are incorporated herein for all
purposes by this reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a control system and a
control method for fail safety of motor driven power steering
(MDPS), and more particularly to a control system and a control
method for fail safety of MDPS by which the type of a fail such as
a self-steering or no-steering situation may be accurately detected
so that the fail safety of the MDPS may be secured.
[0004] 2. Background Art
[0005] A motor driven power steering (MDPS) is mounted on vehicles
that have recently been released to change a steering force of a
steering wheel according to travel speeds of the vehicles.
[0006] The MDPS is a vehicle speed adaptive power steering
apparatus, and functions to provide an optimum steering feeling to
the driver according to the travel speed of the vehicle while an
ECU of the MDPS controls a steering angle and a motion of a motor
according to the vehicle speed of the vehicle.
[0007] As components of the vehicles become electronic, an interest
in the fail safety of the vehicles has increased, and accordingly,
research and development for satisfying IS026262 which is an
international standard has continued even in the field of the
MDPS.
[0008] In order to satisfy the international standards and improve
the fail safety of the MDPS system, an MDPS fail safety measure has
been used.
[0009] The existing MDPS fail safety method is realized by a fail
safety logic that focuses on breakdowns in which an MDPS fail is
expected, such as failure related to a sensor signal mainly input
to the MDPS, an ECU internal circuit, and a motor, and a current to
the motor of the MDPS is immediately interrupted so that the MDPS
operation is stopped without considering an overall state of the
vehicle including the MDPS.
[0010] However, because a fail safety method for monitoring a
function added when a new function of the MDPS is added is
developed through a method suitable for an automotive safety
integrity level (ASIL) and a fail safety logic is added whenever a
function of the MDPS is added, the MDPS fail safety system becomes
complex.
[0011] As various sensors for realizing a fail safety logic are
requested whenever a function of the MDPS is added, manufacturing
costs increase.
[0012] Accordingly, in order to accurately detect a fail of the
MDPS (for example, self-steering or no-steering), the fail needs to
be detected in consideration of an overall state of the vehicle
without adding a separate sensor.
[0013] For reference, the self-steering of the MDPS refers to a
phenomenon [ASIL: D (very dangerous)] in which a high torque is
generated in a motor for MDPS by a fail of the MDPS in a situation
in which an input is not made by the driver (straight motion,
circular turning driving, or the like) and thus the vehicle
unintentionally deviates from a current travel path.
[0014] The no-steering of the MDPS refers to a phenomenon [ASIL: C
(dangerous)] in which the steering itself cannot be made as a motor
torque for MDPS acts reversely while having the same magnitude as
the torque of the driver, in spite of a steering input of the
driver due to malfunction of the MDPS.
[0015] The information disclosed in this Background section is only
for enhancement of understanding of the general background of the
invention and should not be taken as an acknowledgement or any form
of suggestion that this information forms the prior art already
known to a person skilled in the art.
SUMMARY OF THE DISCLOSURE
[0016] The present invention has been made in an effort to solve
the above-mentioned and/or other problems, and an objective of the
present invention is to provide a control system and a control
method for fail safety of MDPS, by which a fail of the MDPS may be
primarily determined and successively the type of the MDPS fail
(for example, a self-steering and no-steering situation) may be
secondarily determined, in consideration of an overall state of the
vehicle, without separately adding sensors, so that the fail safety
of the MDPS may be secured.
[0017] In one aspect, the present invention provides a control
system for fail safety of a motor driven power steering (MDPS), the
control system including: a straight motion/turning determination
module for determining whether a vehicle is in a straight motion or
turning based on a steering angle of a steering wheel, a steering
torque of the steering wheel and a vehicle speed of the vehicle; a
fail determination module for determining whether an MDPS fail
occurs based on a steering torque of a driver and a motor torque of
the MDPS, if the straight motion/turning determination module
determines that the vehicle is in the straight motion; a fail type
determination module for determining a type of the MDPS fail using
a yaw rate change rate, if the fail determination module determines
that the MDPS fail occurs; and a yaw rate change rate detection
module for inputting the yaw rate change rate to the fail type
determination module.
[0018] The control system of the present invention further includes
a motor safety state transition control unit for switching off an
MDPS motor according to determination results of the fail
determination module and the fail type determination module.
[0019] When the vehicle speed is a predetermined value or more, the
straight motion/turning determination module determines whether the
vehicle is in the straight motion or turning based on absolute
magnitudes of the steering torque and the steering angle that have
been input.
[0020] The fail determination module multiplies the steering torque
by the motor torque when the vehicle is in the straight motion to
obtain a calculated value, integrates the calculated value over a
period of time to obtain an integrated value, and determines that
the MDPS fail occurs when the integrated value is a first threshold
value or more and the motor torque of the MDPS increases
non-proportionally to a second threshold value or more at the same
time.
[0021] The fail determination module determines a self-steering
state when the yaw rate change rate is a third threshold value or
more, and determines a no-steering state when the yaw rate change
rate is less than the third threshold value.
[0022] The yaw rate change rate detection module estimates the yaw
rate change rate using the vehicle speed and the steering
angle.
[0023] In another aspect, the present invention provides a control
method for fail safety of a motor driven power steering, the
control method including: determining whether a vehicle is in a
straight motion or turning based on a steering angle of a steering
wheel, a steering torque of the steering wheel and a vehicle speed
of the vehicle; determining whether an MDPS fail occurs using a
steering torque of a driver and a motor torque of the MDPS, if the
straight motion/turning determination module determines that the
vehicle is in the straight motion; and determining a type of the
MDPS fail by detecting a yaw rate change rate, if it is determined
that the MDPS fail occurs.
[0024] The control method further includes switching off an MDPS
motor according to determination results of the fail determination
and the fail type determination using a motor safety state
transition control unit.
[0025] When the vehicle speed is a predetermined value or more,
determining whether the vehicle is in a straight motion or turning
is based on absolute magnitudes of the steering torque and the
steering angle.
[0026] The fail determination includes: multiplying the steering
torque by the motor torque when the vehicle is in the straight
motion to obtain a calculated value; integrating the calculated
value over a period of time to obtained an integrated value; and
determining that the MDPS fail occurs when the integrated value is
a first threshold value or more and the motor torque of the MDPS
increases non-proportionally to a second threshold value or more at
the same time.
[0027] In the fail type determination, a self-steering state is
determined when the yaw rate change rate is a third threshold value
or more, and a no-steering state is determined when the yaw rate
change rate is less than the third threshold value.
[0028] A yaw rate change rate is calculated based on the vehicle
speed and the steering angle signal using
Yaw rate = V x L + K us V x 2 g .delta. f , ##EQU00001##
wherein V.sub.x denotes a vehicle speed, L denotes a wheel base,
K.sub.us denotes an under steer constant, g denotes an acceleration
of gravity, and .delta..sub.f denotes a steering angle.
[0029] Other aspects and preferred embodiments of the invention are
discussed infra.
[0030] It is understood that the term "vehicle" or "vehicular" or
other similar term as used herein is inclusive of motor vehicles in
general such as passenger automobiles including sports utility
vehicles (SUV), buses, trucks, various commercial vehicles,
watercraft including a variety of boats and ships, aircraft, and
the like, and includes hybrid vehicles, electric vehicles, plug-in
hybrid electric vehicles, hydrogen-powered vehicles and other
alternative fuel vehicles (e.g. fuels derived from resources other
than petroleum). As referred to herein, a hybrid vehicle is a
vehicle that has two or more sources of power, for example both
gasoline-powered and electric-powered vehicles.
[0031] The methods and apparatuses of the present invention have
other features and advantages which will be apparent from or are
set forth in more detail in the accompanying drawings, which are
incorporated herein, and the following Detailed Description, which
together serve to explain certain principles of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The above and other features of the present invention will
now be described in detail with reference to certain exemplary
embodiments thereof illustrated by the accompanying drawings which
are given herein below by way of illustration only, and thus are
not limitative of the present invention, and wherein:
[0033] FIG. 1 is a schematic diagram illustrating an exemplary
control system for fail safety of an MDPS according to the present
invention;
[0034] FIG. 2, FIG. 3 and FIG. 4 are flowcharts illustrating an
exemplary control method for fail safety of the MDPS according to
the present invention;
[0035] FIG. 5 is a schematic diagram illustrating a self-steering
situation and a no-steering situation according to a fail of the
MDPS; and
[0036] FIG. 6 is a graph illustrating an MDPS fail determination
time point in the control method for fail safety of the MDPS
according to the present invention.
[0037] It should be understood that the appended drawings are not
necessarily to scale, presenting a somewhat simplified
representation of various preferred features of the present
invention as disclosed herein, including, for example, specific
dimensions, orientations, locations, and shapes will be determined
in part by the particular intended application and use
environment.
[0038] In the figures, reference numbers refer to the same or
equivalent parts of the present invention throughout the several
figures of the drawing.
DETAILED DESCRIPTION
[0039] Reference will now be made in detail to various embodiments
of the present invention(s), examples of which are illustrated in
the accompanying drawings and described below. While the
invention(s) will be described in conjunction with exemplary
embodiments, it will be understood that present description is not
intended to limit the invention(s) to those exemplary embodiments.
On the contrary, the invention(s) is/are intended to cover not only
the exemplary embodiments, but also various alternatives,
modifications, equivalents and other embodiments, which may be
included within the spirit and scope of the invention as defined by
the appended claims.
[0040] FIG. 1 is a schematic diagram illustrating a control system
for fail safety of an MDPS according to some embodiments of the
present invention. FIG. 2 is a flowchart illustrating a control
method for fail safety of the MDPS according to some embodiments of
the present invention.
[0041] First, when a steering angle and a steering torque including
a vehicle speed are input to a straight motion/turning
determination module 10, the straight motion/turning determination
module 10 determines whether the input vehicle speed is a
predetermined value or more (S101), and determines whether the
vehicle is moved straight or turns using the steering angle and the
steering torque (S102).
[0042] That is, when a vehicle speed signal from a vehicle speed
sensor of the vehicle, a steering angle signal from a steering
angle detection sensor for detecting a steering angle of a steering
wheel through manipulation of the driver, and a steering torque
signal from a steering torque detection sensor for detecting a
steering torque of the steering wheel through manipulation of the
driver are input to the straight motion/turning determination
module 10, the straight motion/turning determination module 10
first determines whether the vehicle speed is a predetermined value
or more, and when the vehicle speed is a predetermined value or
more, the straight motion or turning of the vehicle is determined
based on the absolute magnitudes of the steering torque and the
steering angle.
[0043] For example, when the steering wheel is in both a neutral
state (the steering angel of zero) and a state in which the
steering torque is zero, the state of the vehicle is determined as
a straight motion, and when the steering angle and the steering
torque have (+) or (-) values, the state of the vehicle is
determined to be turning.
[0044] Next, when the straight motion/turning determination module
10 determines the state of the vehicle as a straight motion, a step
of primarily determining whether the MDPS fails using the steering
torque of the driver and the motor torque of the MDPS in a fail
determination module 30 proceeds (S103).
[0045] Referring to FIG. 3, in order to primarily determine a fail
of the MDPS, the fail determination module 30 multiplies the
steering torque from the steering torque detection sensor in the
straight motion state of the vehicle by the motor torque from the
motor torque sensor for detecting the torque of an MDPS motor
(S103-1), and integrates the calculated values (S103-2).
[0046] Then, because the steering torque and the motor torque are
proportional to each other, it is determined whether the
accumulated integrated value obtained by multiplying and
integrating the steering torque and the motor torque is a threshold
value or more (S103-3).
[0047] At the same time, it is determined whether the magnitude of
the motor torque instantaneously increases to a threshold value or
more (103-4).
[0048] Accordingly, when the accumulated integrated value obtained
by multiplying the steering torque by the motor torque is a
threshold value or more and the magnitude of the motor torque as
compared with the steering torque instantaneously increased to a
threshold value or more without increasing proportionally, it is
determined that the MDPS fails (S103-5).
[0049] Meanwhile, as illustrated in FIG. 6 illustrating an example
of integrating the values obtained by multiplying the steering
torques by the motor torques over time, when the area of the
accumulated integrated value is a predetermined value or more, it
may be determined that the MDPS fails.
[0050] Next, when the fail determination module 30 confirms that
the MDPS fails, a fail type determination module 40 secondarily
determines the type of the MDPS fail using a yaw rate change rate
(S104).
[0051] Determination of the type of the MDPS fail is to detect a
situation in which a vehicle accident may occur in the MDPS fail
state, and for example, more stable follow-up measures for the MDPS
fail situation may be taken by detecting a self-steering situation
and a no-steering situation.
[0052] Then, the self-steering refers to a phenomenon in which a
vehicle unintentionally deviates from a current travel path due to
a high torque generated in a motor for MDPS by malfunction of the
MDPS while the vehicle is driven straight without an input of the
driver, and the no-steering refers to a situation in which steering
itself is impossible as the motor torque for MDPS acts reversely in
spite of a steering input of the driver due to malfunction of the
MDPS while the vehicle is driven straight.
[0053] Accordingly, if the fail determination module 30 confirms
the fail of the MDPS, the yaw rate change rate detection module 20
receives a vehicle speed and a steering angle, estimates the yaw
rate change rate using Equation 1, and transmits the result to the
fail type determination module 40.
Yaw rate = V x L + K us V x 2 g .delta. f Equation 1
##EQU00002##
[0054] In Equation 1, V.sub.x denotes a vehicle speed, L denotes a
wheel base, K.sub.us denotes an under steer constant, g denotes the
acceleration of gravity (9.81 m/s.sup.2), and .delta..sub.f denotes
a steering angle.
[0055] Subsequently, the fail type determination module 40
secondarily determines the type of the MDPS fail using the yaw rate
change rate from the yaw rate change rate detection module 20, and
the fail type determination module 40 determines a self-steering
state when the yaw rate change rate is a threshold value or more,
that is, excessively high (S104-1) and determines a no-steering
state when the yaw rate change rate is less than the threshold
value, that is, excessively low (S104-2).
[0056] That is, when the yaw rate change rate is a threshold value
or more, a self-steering state may be determined as it is assumed
that the vehicle unintentionally deviates from the current travel
path, and when the yaw rate change rate is less than the threshold
value, that is, excessively low, a no-steering state in which the
steering itself is impossible may be determined in spite of a
steering input of the driver.
[0057] Finally, according to the determination results of the fail
determination module 30 and the fail type determination module 40,
a motor safety state transition control unit 50 performs control to
switch off the MDPS motor.
[0058] That is, when the fail determination module 30 determines an
MDPS fail and the fail type determination module 40 determines the
type of the MDPS fail, the motor safety state transition control
unit 50 performs control to switch off the MDPS motor for
safety.
[0059] In this way, because the MDPS fail may be primarily
determined and the type of the MDPS fail (for example, a
self-steering or no-steering situation) may be secondarily detected
as a problematic situation that may occur due to malfunction of the
MDPS, the problematic situation (the type of the MDPS fail) of the
vehicle may be phenomenologically detected through a vehicle state
monitoring function, and the detection result may be used to
increase a detection coverage for an MDPS fail and efficiently
secure the stability of the MDPS function at the same time.
[0060] Through the above-described problems solution, the present
invention provides the following effect.
[0061] First, a fail of MDPS may be primarily determined and
successively the type of the MDPS fail (for example, a
self-steering or no-steering situation) may be secondarily
detected, in consideration of an overall state information of the
vehicle, without separately adding sensors.
[0062] Second, because an MDPS fail may be determined and
self-steering and no-steering which are accident situations due to
the MDPS fail may be determined, a more stable successive measure
(for example, switching off an MDPS motor) against the MDPS fail
may be taken, and as a result, a functional stability of the MDPS
may be secured.
[0063] The foregoing descriptions of specific exemplary embodiments
of the present invention have been presented for purposes of
illustration and description. They are not intended to be
exhaustive or to limit the invention to the precise forms
disclosed, and obviously many modifications and variations are
possible in light of the above teachings. The exemplary embodiments
were chosen and described in order to explain certain principles of
the invention and their practical application, to thereby enable
others skilled in the art to make and utilize various exemplary
embodiments of the present invention, as well as various
alternatives and modifications thereof It is intended that the
scope of the invention be defined by the Claims appended hereto and
their equivalents.
* * * * *